A brass paperweight is a cylinder of radius 3 cm and height 5 cm with a hemisphere of radius 3 cm fixed on top. Brass has a mass of 8.4 grams per cubic centimetre. Find the mass of the paperweight in kilograms, correct to two decimals. (Take π = 3.14.)

Question

Accepted Answer

1.66. Cylinder = \π r^2 h = (3.14)(9)(5) = 141.3 cm³. Hemisphere = 2/3\π r^3 = 2/3(3.14)(27) = 56.52 cm³. Volume = 197.82 cm³, so mass = 197.82 × 8.4 = 1661.69 g. Since 1 kg = 1000 g, mass = 1.66 kg. 1.19 uses the cylinder only; 2.14 uses 4/3\π r^3 for the hemisphere; 1661.69 leaves the answer in grams while labelling it kilograms.

A brass paperweight is a cylinder of radius 3 cm and height 5 cm with a hemisphere of radius 3 cm fixed on top. Brass has a mass of 8.4 grams per cubic centimetre. Find the mass of the paperweight in kilograms, correct to two decimals. (Take π = 3.14.)

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